creating an ash type disintegration

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  11 November 2012
creating an ash type disintegration

so ive been asked to build an effect that resembles a surface turning to ash,
ive done a point type particle surface emition, no speed , emit via texture ect ect,
looks niice however they would like an ash specific look, before the dissipation the object holds its shape for a few beats, and flutters out into debris..

day three on this, and no luck.
any ideas?..
animated texture emission?
instanced ashes?

anything would help my inspiration

thanks guys^^
  11 November 2012
Something I've done very recently is very similar to this.

I have the particle system goaled to the surface of my object. I have need parent uv checked on the emitter and then I set in the creation expression....

goalU = parentU;
goalV = parentV;

Then I create lots of little mesh objects that are my flake pieces. These are then instanced onto the particle using the standard maya instancer.

In the maya particle shape, under the goal settings, I enable the goalworldNormalPP

I create a maya particle attribute as a vector type and set this value to be the goalWorldNormallPP. So now the vector represents the surface normal. I set the rotation or the aim value (cant remember off the top of my head which one) in the instancer to be this new attr (you might have to check 'allow all types' in the instancer.

The goalWorldNormalPP attr usually works only after the creation frame so you have to step through a couple of frames to see it apply.

Then you can animate goalWeightPP off randomly perparticle to have the pieces be affected by a turbulence field or something and fly off. You'll probably also want to add in some random rotation values to fake the pieces rotating in the air (particles dont have rotation themselves so you have to pass fake rotations to the instancer).

It all takes a lot of careful expression writing but it can be worth it. You'll be able to see an example of it in cinemas soon!
  11 November 2012
thank you for the explanation!!
i will start working immediately on this.
ill post up some wip's when i can,

sounds just rite!!

  11 November 2012
One other thing is in the group of meshes, have one that is an empty transform (no shape information). In the expression editor set the instancer to this blank mesh so that on emission, you dont see the particles in the wrong orientation (because as I said before, the goalWorldNormalPP doesnt activate until after frame creation.

So you will want to on creation, set objectIDPP (or whatever you call it to pass to the instancer) to be this blank one for all particles, then on the runtime expression, set the orientation and give it a object id so that it become visible only when the goalWorldNormallPP sets the mesh to be at the right surface normal.
  11 November 2012
This is what I would do.

Have your original textured geo in main shot. Using SOuP workflow you could animate a bounding object (or several) to delete faces where ever you like, this would take care of your mesh disappearing - no need for transparency maps - therefore making it more flexible.

As the faces are being deleted you could use a SOuP emitter to emit from points via another bounding object (point constrained to the one deleting faces) but slightly larger as to allow for points to emit particles before they are deleted.

From here you are just using instanced particles that are born on the fly and rotating.

With this setup you could also include fluid emission for smoke using the same points for particle emission. To get really fancy you could use density from a fluid to delete faces and emit particles instead of animating a bounding object, this would make things a lot more random. Ill see if I have time to put together a scene or 2 to show you what i mean.
  11 November 2012
maybe you could use Ncloth. shatter up the surface. then combine the pieces. then convert that to cloth. then just use keyed constraints of some sort to start breaking up. then have cool animated texture maps from orig texture to ash texture.

just an idea. good day.
3d is cool!!!
  11 November 2012
thanks for the support guys!
im testing a few things now, hopefully i can chuck a wip up today

again, thank you guys thus far,
  11 November 2012
i would also recommend ncloth. you can have a bunch of 4 point planes textured as ash flakes, maybe even subdivide the planes into 4 faces.

why? well ncloth has lift (force dependent on the orientation of the normal), and lift makes for extremely nice looking tumbling and fluttering that you wont get with a cheated rotation. this would take longer to sim of course so maybe a hybrid of the two would be ideal, instanced particles as a base with hero ncloth ashes upclose.
From Russia, with love @
  11 November 2012
this is going great,
i no longer have the shot, ( now its part of a 2d comic book shot) anyway
having a great time creating this,

however, when using the expression

nParticleShape.goalV += nParticleShape.randV;
nParticleShape.goalU -= nParticleShape.randU;

i get an error on the U and the V...
am i typing this rong?? makes sense to me.

thanks again guys
  11 November 2012
forgot to tell maya what the hell randU and randV ment..heh heh
still isnt the desired crawling across the surface effect i was looking for but, at least therers no error now

  11 November 2012
If you do goalU += randU then every frame it will jump a random amount and look quite eratic. If you have += 0.01 (or whatever constant you want) it will crawl at a contant speed. If you then want it to be more 'random' then the `gauss` function is great as it gives a nice smooth noise that is related though time and not a rand each frame.
  11 November 2012
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